Device for tightening of cables.



(1'. KRAMER. DEVICE FOR TIGHTENING 0F GABLES. APPLICATION FILED APR.16,1908.

91 6,721 Patented Mar. 30, 1909.

UNITED STATES PATENT OFFICE.

,GHBISTIAN KRAMER, OF FRANKFORT-ON-THE-MAIN, GERMANY, ASSIGNOR TO THE FIRM OF FELTEN & GUILLEAUME-LAHMEYERWERKE AKTIEN-GESELLSCHAFT, OF FRANK- FORT-ON-THE-MAIN, GERMANY.

nnvron For. rren'rnnme or CABLES.

No..91e,7'21.

Specification of Letters Patent.

. Patented March 30, 1909.

' Application filed Apr1116, 1908. Serial No. 427,509.

To all whom it may concern:

Be it known that I, CHRISTIAN KRAMER, a subject of the German Emperor, and a resident of Frankfort-on-the-Main, Germany, have invented certain new and useful Imrovements in or Relating to Devices for foundin the transportation of coa or other articles between ships. or between a ship and the shore, the transportation being effected by means of a vehicle and cables which at one end are secured'to' the ship and at the other-end aresecured to another ship'or the shore as the case may be. It will be apparent that under the circumstances just referred to, the rolling of the ship or ships will varythe distance between them and, 1n case provision to avoid it were not made, the tension of the cables would be alternately slackened and tightened as the points came closer togetheror were moved farther from each other. It is generally necessary, in appara-' tus of the character described, that the transportation cables should have practically a constant tension.

One object of the present invention is to regulate the tension by means of an automatically operating motor which may be designated as a stretching motor.

Another object of the invention is to so connect the stretching motor that it will have a regulating action upon the circuit of the driving motor.

Another object of the invention is toprovide a stretching motor of such type that the energy losses therein will be a minimum.

Another object of the invention is to provide a driving motor which will maintain practically constant speed of the ,cable even though the voltage impressed upon the driving motor ma be varied.

The invention is'illustr'ated in the accompanying drawing which is a diagram showing the electrical connections and the relations of the mechanical parts. 4

' Referring to the drawing, the endless convey'er cable a passes over the two rollers or drums b and 0, one. of these rollers I being mounted at oneof the points between which transportation is to be effected, as a slnp,

while the other 'is located at the other of those points which may be another ship or the shore. The endless cable a is also caused to form a loop by passing over the pulleys (l, e and f. The pulley f is free to move under the influence of a cable 0'. adapted to be, wound upon or unwound from a drum h, it being obvlous that as the cable t is unwound the ten- P sion upon the driving cable a will be relieved while when the cable 2' is wound up any. slack in the cable a will betaken up.

.. One of the drums b or. c, in this case 0, is

driven by a motorg. This motor is of -the shunt type and is self excited, its field belng connected across the terminals of the arms.

ture as shown. It will be a parent that an change of voltage across tie armature wil also afiect the field with the result that a practicallyuniforrii speed will be maintained even though the voltage appliedto the terminals, of the motor may vary. The desirable end of maintaining the speed of the conveying cable practically constant is therefore attained. Mechanically connected with the drum h is a series motor which is connected in series with the-driving motor 9 between the mains 1 and 2. The term series motor is used with the meaning well understood in the art, namely, that the field is connected in series with the armature, as shown. It will be apparent that the current supplied by the mains 1 and 2 to the driving motor 9 will pass through the motor 76 and thereby a torque .will be developed in the motor is. The parts of this motor are so arranged and connectedthat this torque tends to wind up the cable '11 u on the drum it so as to hold the conveying ca 1e a in tension. During normal operation of the apparatus the motor 7r resistance of its winding, which, as it is wellknown, is small in a series motor. If now the drums b and a move closer together, and

slack thereby caused in the'cable a, the torque in the stretching motor 7 will cause it to rotate as a motorto take up the slack, this action taking place automatically. The 0 oration of the motor 7c however, as descri ed, causes a counter electro-motive force to be developed which opposes the electro-motive force of the mains 1 and 2 with the result that the momentary tendency of the driving motor to speed up upon the throwing oil" of the load is counter acted. The operatiomof the stretchingmotor continues as just described until the tension ol the cable has been increased ,to such an extent as to counterbalance the torque of the stretching motor. On the other hand if the drums b and c are more widely separated the torque of the motor 7c will be overcome and it Wlll be driven as a dynamo, its electro motive force being added to that of the mains land. 2, the sum of these electromotive forces being impressed upon the driving mo-' tor g. This operates to counter-act the momentary tendency of the driving motor to slow down upon the sudden throwing on of the load. -'I re motor 7c continues to be driven as a dynamo until its torque becomes counter-balanced by the tension of the cable when it comes to rest. It will now be apparent that the motor 7c operates to automatically regulate the circuit of the driven motor and this without the interposition of resistance or other devices which are wasteful of energy.

It is further to be noted in connection with the present invention that no special form of motor is necessary but that the usual com mercial motors may be employed.

What I claim is 1. In a device of the character described,

the combination with a cable of an electric motor for driving the same and an electric motor for automatically maintaining the tension of said cable,-said motors being connected in series.

2. In a device a; the character described, the combination'with a cable of an electric motor for driving the same and an electric motor for automatically maintaining the tension of said cable; said motors being connected in series, said driving motor having its field connected across the termmals of 1ts armature.

3. In a device of the character described,-

the combination with a cable, of an electric motor for driving the same and a series motor for automatically maintaining the tension of said cable, said motors being connected in series.

4. 'In a device of the character described, the combination of'a cable, a driving motor therefor having its field connected across the 

